Method for electrodeposition of iron in the form of continuous strips



March 4, 1952 E. H. KONRAD EIAL METHOD FOR ELECTRODEPOSITION OF IRON IN THE FORM OF CONTINUOUS STRIPS Filed July 28, 1949 Patented Mar. 4, 1952 METHOD FOR- ELECTRODEPOSITIO N- OE IRON IN THE FORMOF CONTINUOUS STRIPS- Erich H. Konrad, Shelburne, and William E. C. Eustis, Burlington, Vt., assignors to sulphide Ore Process Gompan corporation of Delaware y, Inc., New York, N. Y., a

Application July 28, 1949, Serial No. 107,334

3 Claims.

The-present invention relates to anew and useful improvement in the process of producing electrolytic iron, directly from the natural ores of iron, in the form of a continuous strip which is continuously removed from the cathode by mechanical'means;

By this process, iron is taken into solution from sulphide ores of iron, and is discharged from the operation in the-form of a continuous strip of pure' ductile iron that may be wound into coils for shipment. Thereisno intermediate operation upon the solid ore or upon the solid iron, but only mechanical handling of solutions, from the time when the ore is fed to the solution tanks until the metallic iron is removed as a continuous strip or sheet. The process of the invention enables one to operate with a small consumption of electric energy, with very little energy in the form of heat, and with only small mechanical and chemical replacements.

It is old in this art to produce strips of iron from soluble anodes composed of free metallic iron. But we believe we are the first to. produce continuous strips of iron direct from the sulphide ores of iron.

The process of the invention includes the preliminary provision of a ferrous iron solution containing a freely sol'uble'ferrous salt (such as ferrous chloride or ferrous sulphate) followed by the electrolytic deposition of metallic iron from the ferrous salt solution upon a continuous cathode surface; in the formi of a continuous, integrated sheet or strip of flexible metalliciron, which is maintained separable from the cathode surface, and separating (preferably uniformly and continuously) the continuous iron strip from the catho'desurface: The process also includes 'simul taneouslywithdrawing the anolyte from the'electrolyte adjacent to the anode, which constitutes an aqueous solution of ferric salt, (for example, preferably at least 4O grams per lite'rbut not over 100 grams of iron, per liter, as the chloride)c'on tactin'g'fresh quantities'of iron sulphide ore therewith, to reduce the solution to the ferrous condition, generating hydrogen sulphide therein, there'- by'precipitating insoluble sulphides, degasifying the solution, and cycling the resulting purified ferrous ironsolution to-the catholyte, preferably adjacent to-the cathode surface, for continued electro-deposition of the metallic ironstrip;

A typical and representativeexampleof the invention will be described, with reference to" suitable apparatus for its industrial application, as illustrated in the'ac'companying' drawings, in which: I

2 Fig. l is a diagrammatic elevation and crosssectional view of the complete apparatus for carrying out the process of the invention;

Fig. 2 is an enlarged, longitudinal cross-sectional view of the anode and its appurtenant arrangements;

Fig. 3 is a cross-section, in elevation, of a modified form of the electrolytic cell or tank, which may be used in conjunction with the apparatus shown in Fig. 1;

Fig. 4- is a plan view of the tank shown in Fig. 3; and

Fig. 5 is anisometricprojection of a corner of the tank shown in Fig. 3 to illustrate the mounting of the porous anode bars therein.

In the apparatus shown in Fig. 1, an electrolytic cell or tank I is provided withv a pair. of graphite anodes 2 and a cathode 3, which is. in the form of a cylinder which canbe slowly r0,- tated in the direction as indicated by thearrow, by means, of any suitable mechanism for this purpose. (not shown) about its longitudinal axis l; Diaphragms in the form of suitable chemical- 1y resistant screening 5 and cloth bags 6 (seeFig. 2). surround each of the anodes,. and enclose chunks of graphite 7' (preferably coarse, about inch. in diameter) which are interposed between thebag and the anode, on thatside of each anode which is disposed towardthe cathode. Pipes 8, are-provided which lead down into each of. the-i-anodebags to apoint-near the lower end of .the anode for withdrawing the anolytefrom the vicinity of the anode surface and of the chunks-of graphitewithin the bag. The pipes 8 syphon theanolyte to a storage tank. 9. The anolyte is conducted to a solution tank In, as required,.which isprovided with a stirrer II- and a supply means I2 for delivering finely ground orethereto. (In this tank both leaching and purification of metallic ions are accomplished.) The solution tank Iii is followed by a pump. l3 through filter I l to a degasification tank [5, in. which the leach liquor. from tank I!) is degasifled. and from which the purified solution may be, withdrawn by pump I 6, and delivered through the'filter l1, and thence to the head tank ifl'from which it is led, through the constant level device 89, such as a float valve'into the electrolytic cell or tank I. 20 is a rectifier for supplying direct current to the cathode and anodes of the cell;

Using the-apparatus shown in Fig. 1, a continuous strip of so'ft ductile electrolytic iron-was produced direct from pyrrhotite one which had a. composition of 55.5% Fe, 36.1% S, 0A3 '73: Cu,

placed between it and the anode bar, on

then enclosed in the spool 25, upon which wound into a coil as formed, in a continuous thin "strip or sheet.

and about 8% of gangue material, as silica, lime and magnesia.

The cathode 3 consisted of a wheel made of steel having a face 7.0 inches wide and a diameter of 24 inches. The inside surfaces of the wheel and its spokes and axle were coated with chemically resistant cement to prevent corrosion and to make the surfaces, other than the face of the wheel, electrically non-conductive and thus prevent the deposition of iron thereon. The active surface of the periphery of the wheel, or cathode, was lightly but uniformly coated with a colloidal solution or suspension of graphite. The edges of the cathode surface were painted with an acid-resistant varnish to prevent edge deposits.

Each of the anodes consisted of a bar of solid graphite measuring 40.5 inches long, 7 inches wide and 1.1 inches thick. These bars were inclined at an angle of 45?, positioned on opposite sides of, parallel to and beneath the cathode surface which was mounted with its axis horizontal, as shown in Fig. 1. Each of the anode bars was surrounded with a bag or envelope which was made of vinylidene chloride insect screening of suflicient size to allow one layer of the pieces of the crushed graphite I to be the side of the anode bar next to the cathode. In this instance, pieces of the crushed graphite were not used on the side of the bar away from the cathode. The anode, as thus assembled, was a diaphragm bag 6, made of vinylidene chloride.

The cathode had a smooth steel surface which was initially coated with a thin film of a colloidal dispersion of graphite by wiping it on with a cloth.

(It may be similarly applied automatically as by a wick or sponge 2| and gravity fed from a reservoir 22.)

The cathode drum was rotated at a speed of one turn in 2.56 hours. It was turned by an electric motor of /.;,'horsepower, operated at a speed of 1750 R. P. M. which was connected by a 3:1 belt reduction to two 300 to 1 gear trains, connected in series and then directly coupled to the axis of the cathode. This gave a peripheral speed at the surface of the cathode which was slightly in excess of one-half inch per minute.

Direct current was first applied through the rectifier 20, so as to make the drum the cathode, and the carbons the anode, and to provide a current density of 86 amperes per square foot of the wetted cathode surface resulting in a potential drop across the cell of about 4 volts.

The electric current was applied for about one hour, keeping the cathode stationary; then, when a suitably continuous and integral layer of iron had been built up-and of a sufficient thickness and strength to permit removal-the cathode drum 3 was started to rotate, in the direction of the arrow as shown in Fig. 1. The advancing edge ofthe deposited metal 23 was separated from the cathode drum, as it emerged from the electrolyte and led slowly over the guide roll 24 to it was taken up. and

The free surface of the cathode drum, above the solution, was continuously prepared to re- ,ceiver a fresh deposition of electrolytic iron, by

coating with a suitable amount of colloidal graphite, throughout the operation of the cell. This was applied, as initially, by wiping with a cloth. The acid-resistant varnish on the edge was also renewed after stripping.

The electroplyte, provided from the supply tank l8 to maintain a constant level in the cell l, contained I29 grams per liter of ferrous iron, as ferrous chloride, with only a trace of ferric iron, and had a pH value of 1.43 as fed into the catholyte.

The anolyte was withdrawn from the interior of the anode bags adjacent to the surfaces of the anodes and graphite chunks therein, near the bottom, through pipes 8, at the rate of 1'70 c. 0. per minute. As thus withdrawn, the anolyte had a composition of 145 grams per liter of ferrous iron as ferrous chloride and 28 grams of ferric iron per liter as ferric chloride. This high concentration was consistently found to exist and was ascribed to evaporation from the rather great surface of the electrolyte, at the very high temperature of operation.

The temperature of the cell at the commencement of operations as above described, was C.

When the rotation of the cathode was commenced (i e., about anhour after preliminary deposition had been effected with the cathode stationary), the current was amperes and the temperature was still 90 C. After 2% hours of operation, the temperature of the electrolyte had risen to 94 C. The current was then 148 amperes and the voltage drop between the anodes and cathode 4.05 volts. At the end of 7 hours the current was still 148 amperes and the voltage drop between the anodes and cathode was 3.8 volts, while the temperature was 96 C.

The run was discontinued (although in full successful and satisfactory operation) after 8.75 hours of continuous operation, in which a continuous, integral uniform strip of electrolytic sheet iron was produced.

Since the cathode was stationary for the first hour, it turned for only 7.75 hours. In this period of rotation the cathode turned 3.03 revolutions and produced 19.0 lineal feet of strip. Three feet were clipped from the lead end of the strip andone foot was cut from the tail end. This left a continuous piece 15 feet long. The thickness of the strip was .0034 inch. The metal was smooth, dense and ductile. A sample clipped from this sheet could be bent around a six penny nail, without breaking. Such a nail measures .115 inch in diameter.

During the electrolysis, the anolyte, as withdrawn continuously through pipes 8, was allowed to accumulate in the tank 9, and after the electrolytic deposition of iron therefrom was stopped,

this withdrawal of the anolyte was continued until substantially all of the ferric iron had been removed from the cell i. The amount of anolyte thus collected was 32.5 gallons.

This anolyte was fed into the solution tank 10 which measured 3 feet in diameter and 4 feet deep. It was in all respects satisfactory to use as a leaching solution, per se, but in the instant-case the tank 10 was filled to the gallon level with this solution plus similar anolyte solutions obtained from other operations, and heated to 105 C., with live stream. It may be noted that the anolyte produced from these other operations was higher in ferric ion concentration, since both sides of the anodes were in use as compared with one side in the instant case. Pyrrhotite ore, to the extent of 51.8 pounds, moist weight (13% moisture) was added. This was suflicient to reduce the 150 gallons of ferric solution completely to ferrous solution. A sumcient concentration of hydrogen: ion was. present so that after complete reduction of theferric chloride, some of the pyrrhotitewas reacted upon by the free acid, to

liberate hydrogen sulphide, in an amount sufiicient to precipitate the copper-group metals present, as their corresponding insoluble sul- 150 gallons. of solution were then pumped. via

pump l3 through filter l4 into tank I5 and aerated therein, until all traces of gaseous hydrogen sulphide had been expelled. A little activated. charcoal was added in this step to facilitate degasifying. When this operation had been completed, the solution was returned to storage tankl8 via filter I! by pump Hi.

It was desirable, if not necessary, to keep the anode onthe side of the cathode drum which was entering the electrolyte, as close as practicable-to the cathode surface of the drum. The angle: of the anodes was changed and adjusted to accomplish this. Otherwise at the entrant portion of the cathode surface, where the formation of the deposit of electrolytic iron begins, a troublesome spraying of the electrolyte occurs and a poor deposit'of iron results.

The edges or the drum cathode must be suitably protected by non-conductive material to avoid. the formation of' trees. This may be done by painting the edges with a coating. of rubber, or by applying edge. pieces of wood or acid resistant resinous materials, as well as with varnishj as above mentioned, or like treatment.

The anodes should preferably be slightly narrower than the surface of the drum cathode to which they are opposed, to avoidtreeing and overlapping of the deposit.

The thickness of the strip of electrolytic iron which is to be deposited may be controlled by varying the current density or by varying the rate of rotation of the drum cathode, or both. But it. must be so regulated and controlled (preferably continuously and uniformly) that the deposited metal shall form a continuous, integral metallic sheet of predetermined and constant dimensions and properties- An improved form of the apparatus is shown in Figs. 3 to 5, which is characterized by making the anode conform to the shape of the cathode and by a provision for separating the catholyte from the anolyte by a pervious anode (instead of a diaphragm) through which the catholyte may pass continuously, thereupon to constitute the anolyte, which may thus be segregated and withdrawn as above described. As previously, however, it may be expedient to have the anode surface slightly narrower'than the cathode surface to avoid treeing of the deposited metal over the margins of the cathode surface.

Referring to Fig. 3, the electrolytic cell may comprise a, tank 26, which is provided with end walls 21, each having a member 28 presenting an upwardly disposed semi-circular surface 29 and a semi-circular channel 30, in the inner margin thereof. The anode 3| as a whole is made up of rectangular strips of pervious carbon or graphite 32, 32 the ends of which rest upon the semi-circular channel 30, and the inner surfaces of which constitute a substantially uniform cylindrical surface, flush with the semicylindrical surfaces 29. The abutting margins and ends of the anode strips 32, 32, may be joined together and made liquid-tight b means of an electrically conductive cement at the joints 33, 33, etc. Alternatively, if desired, the semipermeable or pervious anode strips 32, 32, may be machined to form a truly cylindrical surface and to form water-tight joints, each to each and at the ends, without the use of cement. But this is not necessary for ordinary purposes of construction and operation.

The end or uppermost anode strips may advantageously extend above the surface of the electrolyte or catholyte 34. Metallic contacts are fastened to the anode I to connectwith the lead wires from the rectifier 20.

The cathode 36 is cylindrical, as in Fig. l, and mounted for rotation about its horizontal axis mounted at 37, preferably concentric to the inner cylindrical surface of the anode 3| and with the cathode surface evenly spaced therefrom. The cathode is rotated by any convenient mechanism, such as the pulley 38 and belt 39. in the direction of the arrow, and slowly" but preferably uniformly, at least after the initial deposition of an integral sheet of iron thereon. The deposited metallic sheet of iron dil is gradually advanced, by rotation of the cathode, in the direction of the arrow and thence separated and carried over a guide roll 4| and thence under a guide roll 42, submerged in wash water bath- 43 in the tank 44, and thence to the takeup roll 45.

In operation, the tank 26 may therefore replace tank l, of the apparatus shown in Fig. 1, suitable connection being made from the electrolyte supply reservoir l8 through float valve |9 or like control means, into the catholyte compartment'dfi adjacent to the cathode 36, and within the semi-cylindrical annular chamber formed between it and the upper semi-cylindrical surface of the anode 3|. The outer or'anolyte compartment 41, between the outer cylindrical surface 48 of the anode 3| and the inner walls and bottom of the tank 26, is connected to outlet pipes 8 (as in Fig. 1) leading by gravity to the anolyte storage reservoir 9, or directly to the leaching tank H].

The operation of the process with the apparatus as thus provided and arranged is substantially as described above with reference to. the apparatus illustrated in Figs. 1 and 2. They level of the catholyte 35' is maintained positively above the level of the anolyte 41.

We claim:

1. Method of converting sulphide ores of iron into a continuous strip of metallic iron, which comprises the steps of providing an electrolytic cell comprising a cylindrical cathode having a substantially continuous electrically conductive cathode surface formed of particles of colloidal graphite, an insoluble anode enclosed in a porous diaphragm and an electrolyte therein comprising a catholyte containing a ferrous salt, substantially free from ferric salts, and an anolyte, containing a ferric salt, the anode being in opposed relation to the submerged portion of the cathode in the electrolyte bath, setting up an electric potential between 'the cathode and the anode, thereby to effect a preliminary deposit of electrolytic iron upon the cathode surface, then rotating the cathode surface continuously into, through and out of the catholyte, to thereby effect electrodeposition of ductile metallic iron upon the cathode surface in the form of a continuous integral strip, simultaneously Withdrawing the anolyte from within the diaphragm adjacent the anode, contacting the anolyte with 7 the sulphide ore of iron, thereby to reduce the anolyte to the ferrous condition and replenish the ferrous iron content and cycling the resulting solution into the catholyte, continuously separating the metallic iron from the cathode, as a continuous strip and continuously applying a coating of colloidal graphite to the cylindrical cathode surface as the same is exposed out of the bath.

2. Method of converting sulphide ores of iron into a continuous strip of metallic iron,,which comprises the steps of providing an electrolytic cell comprising a cylindrical cathode having a substantially continuous electrically conductive cathode surface formed of particles of colloidal graphite, an insoluble anode enclosed in a porous diaphragm and an electrolyte therein comprising a catholyte containing ferrous chloride, substantially free from ferric chloride, and an anolyte, containing ferric chloride, the anode being in opposed relation to the submerged portion of the cathode in the electrolyte bath, setting up an electric potential between the cathode and the anode, thereby to effect a preliminary deposit of electrolytic iron upon the cathode surface, then rotating the cathode surface continuously into, through and out of the catholyte, thereby to effect electrodeposition of ductile metallic iron upon the cathode surface in the form of a continuous integral strip, simultaneously withdrawing the anolyte from within the diaphragm adjacent the anode, contacting the anolyte with the sulphide ore of iron, thereby to reouce the anolyte to the ferrous condition and replenish the ferrous iron content and cycling the result ing solution into the catholyte, continuously separating the metallic iron from the cathode, as a continuous strip and continuously applying a coating of colloidal graphite to the cylindrical cathode surface as the same is exposed out of the bath.

3. Method of converting sulphide ores of iron into a continuous strip of metallic iron, which comprises the steps of providing an electrolytic cell comprising a cylindrical cathode having a substantially continuous electrically conductive cathode surface formed of particles of colloidal graphite, an insoluble anode enclosed in a porous diaphragm and an electrolyte therein comprising a catholyte containing ferrous chloride, substantially free from ferric chloride, and an anolyte, containing ferric chloride, the anode being in opposed relation to the submerged portion of the cathode in the electrolyte bath, setting up an electric potential between the cathode and the anode, thereby to effect a preliminary deposit of electrolytic iron upon the cathode surface, then rotating the cathode surface continuously into, through and out of the catholyte, thereby to effect electrodeposition of ductile metallic iron upon the cathode surface in the form of a continuous integral strip, while keeping the anode surface as close as practicable to the opposed portion of the cathode surface entering the electrolyte, simultaneously withdrawing the anolyte from within the diaphragm adjacent the anode, contacting the anolyte with the sulphide ore of iron, thereby to reduce the anolyte to the ferrous condition and replenish the ferrous iron content and cycling the resulting solution into the catholyte, continuously separating the metallic iron from the cathode, as a continuous strip and continuously applying a coating of colloidal graphite to the cylindrical cathode surface as the same is exposed out of the bath.

ERICH H. KONRAD. WILLIAM E. C. EUSTIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,412,174 Eustis et a1 Apr. 11, 1922 1,416,692 Dantsizen May 23, 1922 1,456,615 Belcher et a1. May 29, 1923 1,952,762 Levy et a1. Mar. 27, 1934 1,960,563 Wilkins May 29, 1934 1,980,381 Cain Nov. 13, 1934 2,429,902 Sternfels Oct. 28, 1947 FOREIGN PATENTS Number Country Date 8,668 Great Britain of 1912 OTHER REFERENCES Plating, January 1948, pages 45,46. 

1. METHOD OF CONVERTING SULPHIDE ORES OF IRON INTO A CONTINUOUS STRIP OF METALLIC IRON, WHICH COMPRISES THE STEPS OF PROVIDING AN ELECTROLYTIC CELL COMPRISING A CYLINDRICAL CATHODE HAVING A SUBSTANTIALLY CONTINUOUS ELECTRICALLY CONDUCTIVE CATHODE SURFACE FORMED OF PARTICLES OF COLLOIDAL GRAPHITE, AN INSOLUBLE ANODE ENCLOSED IN A POROUS DIAPHRAGM AND AN ELECTROLYTE THEREIN COMPRISING A CATHOLYTE CONTAINING A FERROUS SALT, SUBSTANTIALLY FREE FROM FERRIC SALTS, AND AN ANOLYTE, CONTAINING A FERRIC SALT, THE ANODE BEING IN OPPOSED RELATION TO THE SUBMERGED PORTION OF THE CATHODE IN THE ELECTROLYTE BATH, SETTING UP AN ELECTRIC POTENTIAL BETWEEN THE CATHODE AND THE ANODE, THEREBY TO EFFECT A PRELIMINARY DEPOSIT OF ELECTROLYTIC IRON UPON THE CATHODE SURFACE, THEN ROTATING THE CATHODE SURFACE CONTINUOUSLY INTO, THROUGH AND OUT OF THE CATHLOYTE TO THEREBY EFFECT ELECTRODEPOSITION OF DUCTILE METALLIC IRON UPON THE CATHODE SURFACE IN THE FORM OF A CONTINUOUS INTEGRAL STRIP, SIMULTANEOUSLY WITHDRAWING THE ANOLYTE FROM WITHIN THE DIAPHRAGM ADJACENT THE ANODE, CONTACTING THE ANOLYTE WITH THE SULPHIDE ORE OF THE IRON, THEREBY TO REDUCE THE ANOLYTE TO THE FERROUS CONDITION AND REPLENISH THE FERROUS IRON CONTENT AND CYCLING THE RESULTING SOLUTION INTO THE CATHOLYTE, CONTINUOUSLY SEPARATING THE METALLIC IRON FROM THE CATHODE, AS A CONTINUOUS STRIP AND CONTINUOUSLY APPLYING A COATING OF COLLOIDAL GRAPHITE TO THE CYLINDRICAL CATHODE SURFACE AS THE SAME IS EXPOSED OUT OF THE BATH. 